Gabby Williams scored eight points in overtime as the Golden State Valkyries completed a three-game sweep of the defending champion Las Vegas Aces with an 87-77 road victory on Friday, advancing to the WNBA finals in only their second season as an expansion franchise.

After a Golden State run in the final three minutes of the fourth quarter forced overtime, the Valkyries outscored the Aces 16-6 in the extra period to secure the series in convincing fashion.

“Obviously it feels good, especially to beat the defending champs,” Golden State’s Kiah Stokes said. “They’re a team that can get hot real quick, and I think we didn’t want this to go to Game 4, Game 5, because like I said, they’re defending champs. They’ve been in this position, you don’t really want to give them any life.”

The second-seeded Valkyries will face the fourth-seeded Atlanta Dream, who clinched a finals berth with an 85-83 road victory over the New York Liberty on Friday to complete their own sweep. Game 1 of the finals is scheduled for 17 October in San Francisco.

Trailing 69-63, the Valkyries went on an 8-0 run and took a 71-69 lead on a basket from Veronica Burton with 1:12 remaining in regulation.

Las Vegas’s Jackie Young tied the game at 71 on a layup assisted by Chelsea Gray with 26.6 seconds left. After Williams missed a layup attempt with five seconds remaining, Gray’s 15ft shot at the buzzer narrowly rimmed out.

The Valkyries opened overtime with a 12-2 run that featured eight points from Williams, establishing an 83-73 lead with 46.9 seconds remaining.

Kayla Thornton led the Valkyries with 18 points and nine rebounds, shooting five of 12 from the field and six of seven from the free-throw line. Williams added 16 points on six-of-16 shooting, while Hayes and Stokes scored 11 apiece.

Stokes shot five of five from the field, grabbed 10 rebounds and played effective defense against Aces star A’ja Wilson.

“I can get emotional talking about [Kiah],” Williams said. “Honestly, she’s just someone that is so appreciated by us. Everything she does, she just knows how to win. There’s a reason she’s a three-time champion. I’ve said it a million times. ... Offensively, the way she sets screens, the way she moves without the ball, the way she gets all these offensive boards and extra possessions. Defense, I don’t think I have to say anything. We know who she is.”

Wilson, who won her record fifth WNBA most valuable player award this week, led the Aces with 21 points and 10 rebounds but shot just six of 19 from the field. Young added 16 points on six-of-16 shooting, while Gray finished with 17 points and a team-high five assists. Gray also committed a game-high six turnovers.

“If you want to win championships, you need to be a top-three, top-four defense, and we weren’t this year,” Aces coach Becky Hammon said. “We weren’t. We had moments where we were pretty good, but we weren’t good enough to be at a championship level. You got to be clicking on all cylinders on both ends, and we were not.”